Electric guitar bridge



Aug. 6,'1968 R. c. scHERER ELECTRIC GUITAR BRIDGE Filed Aug. so, 1965 lil INVENTOR ROBERT C. SCHERER mwa- United States Patent Ohio Filed Aug. 30, 1965, Ser. No. 483,679 Claims. (Cl. S10-8.3)

The present invention relates generally to transducer bridges for stringed instruments, and more particularly to transducer bridges capable of bearing the tensions of the strings of `stringed instruments and of providing an electrical signal in response to vibra-tions of the strings.

Electric guitars are conventionally provided with transducers, capable of providing output in response to the vibrations of the strings when the latter are picked or plucked. In such guitars the modes of vibrations of the strings vary with time, from initial excitation to final decay, and, in particular, picking or plucking a string may induce a vibration in one plane in space while the free vibrations of the string may be in another plane, or the plane may oscillate in space depending on the precise character of the excitation.

Guitar players Vdesire that the sound of an electric guitar be similar to that of an acoustic guitar, but the conventional electromagnetic transducers employed in electric guitars are no-t capable of responding to all planes of vibration of a string, and usually can respond only to vertical vibrations, whereby the initial excitation of the string, which is predominately horizontal, is lost. Nor can such transducers opera-te in conjunction with nylon or other non-metallic strings.

It is a function of the present invention to provide a string transducer, especially for an electric guitar, which responds to vibrations of a string occurring in any plane, and which responds equally well to metallic and nonmetallic strings.

Brieily describing a preferred embodiment of the invention, an elongated metallic extrusion is provided, having the cross section of a U. One arm of the U forms a base which is supported on the body of a guitar, at the usual bridge location. The other arm is arranged to provide plural cantilever arms, for separately supporting each strin-g of the guitar. Considering one string only, for simplicity of explanation, a piezo-electric crystal is placed between the base and a cantilever arm, Underlying the crystal is a thin sheet of copper, i.e., Ishim stock or the like. Underlying the latter is a sheet of insulation which has acoustic damping properties, and underlying the latter, in contact with the extrusion, is a `further thin sheet of copper, i.e., shim stock or the like. rlhe two copper sheets then provide electrodes for the crystal and can be conveniently connected to output leads.

The strings of a guitar are connected, adjacent the bridge, to a tremolo bar. This is a lever operated device for simultaneously manually varying the tensions of all the strings of the guitar, whereby the player can produce modulation of tonal output. A longitudinal movement of the strings occurs during manipulation of the tremolo bar, which would saw across the lbridge if the latter were immovable. The bridge is accordingly mounted to pivot freely on an axis transverse to the strings.

According to the present invention, two holes are provided near the ends of the base of the extrusion. Threaded pins extend upwardly from a base plate and freely through the holes, and thumb nuts are provided on the screws, as adjustable supports for the base of the extrusion. The thumb nuts have tapered portions which mate with the hole edge and which form bearings for the holes, permitting the extrusion to pivot freely.

It is an object ofthe invention to provide a novel and economical pivotable transducer bridge for an electric guitar.

As a further feature of the invention, the transducer system of the invention is provided with string bearing elements which are adjustable in the direction of string length, individually for each string, to compensate the individual guitar for the differences from true pitch which ensue when the strings are stopped to short lengths, as a function of mechanical parameters of the string, such as density, thickness, etc.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following -detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is a view in perspective of a guitar embodying the present invention;

FIGURE 2 is a view in perspective of a bridge transducer and mounting according -to one embodiment of the invention;

FIGURE 3 is a view in transverse section taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a further view in transverse section taken on the line 4--4 of FIGURE 2;

FIGURE 5 is a view in plane of a modied form of the transducer of FIGURE 2; and

FIGURE 6 is a view in transverse section taken on the line 66 of FIGURE 5 Referring now to the accompanying drawings, 10 is an elongated extrusion, which may be made of aluminum, brass, `or the like, and which has a U shape when taken in cross section. Arm 11 of the U is a base arm, and contains holes 11a adjacent to its ends, which are located symmetrically of the width of the base 11, and serve for pivotably supporting the `base yon nuts 12 threadedly engaging two threaded pins 13. The further or upper arm 14 of the extrusion is provided with transverse slots 15, which extend into the end wall 16, of the U, and form plural cantilever arms 14a. An inverted V-shaped riser 17 is provided near the forward edge of each arm 14a, `which has 4a transverse notch 18 cut at its center. The notches 18 serve to locate guitar strings S.

The cantilever arms form individu-al supports for the strings, which are acoustically largely isolated from one Ianother by the slots 15.

Located under each cantilever arm 14a is la piezoelectric crystal 20, having one wall in contact with the under side of the arm 14a, Under the crystals is a strip of thin shim stock 21 slotted at 21a, under each of slots 15. vUnder each strip of shim stock 21, is a strip 22, of insulation, which is resilient mechanically and which `clamps acoustic vibrations. Underlying the strip 22, is a further strip of shim stock 23. Strip 22 thus forms one electrode for all of crystals 20, and strip 23, grounded to the extrusion, forms the other electrode. Leads 25 are connected to strips 21 and 23.

A base plate 27 underlies the base 11. From the base plate 27 extend the threaded pins 13, which are located to mate with holes 11a and to extend freely therethrough. On the pins 13, are threadedly engaged knurled thumb nuts 12, hav-ing central tapered risers 28 which serve as balls to engage the holes 11a, and to permit pivotal movement of the base plate 11 with respect to base plate 27. Adjustment of Ithurnb nuts 12 vertically permits leveling of the bridge transducer as a whole, and adjustment of its vertical position with respect to the body of the guitar.

In the system of FIGURES 5 and 6, an elongated extrusion 30 is employed, which is of U-shaped cross section, as in the system of FIGURE 1, and integrally includes a base [arm 31, a string support arm 32 and a joining element 32a for the arms. The lengthwise edges 33 of the extrusion are cut at an angle of about 84 t-o the end edges 34. The support arm 32 is provided with grooves 35 in pai-rs, defining a cantilever `arm 35a each containing a central land 36. The grooves 35 extend parallel to the end edges 34, and for the entire width of the sup.- port arm 32 and Well into joining element 32a. On the cantilever `arms 35a, guided Vby lands 36, slide string supiports 37, each -consisting of a transverse raised member 38 and a pair of arms 39, 40 extending from the transverse 'raised member 38 at right angles thereto. The arms 39, 40 snugly tit the sides of the land 36 and are slidable thereon, while the transverse raised member 38 straddles and slides on land 36. As illustrated in FIGURE 6, a string 40 of a guitar is located in a notch 41 cut centrally of the transverse raised member 38. Each pair of arms, as 39, 40, is held in position, once it has been properly located by a bolt 42, which threadedly engages a threaded opening in the land 36. The bolts, having wide heads 43 which extend over the arms 39, 40, lock these in place when the bolt is tightened.

'Crystals and electrodes therefor are located and function as in the system of FIGURE 1. The 84 angle which the lengthwise edges 33 make with the directions of the guitar strings, and the Iadjustability of the string suplports of the lever arms, enable the adjustment of the bridge string termination such that the string plays in tune over its entire playable range, regardless of its physical parameters pertaining to oscillatory frequency.

It is a feature of the present invention that the guitar may utilize metallic or non-metallic strings, i.e., nylon or steel, throughout yor in part, without effect on tonal output, insofar as this effect may be due to the transducer.

The use -of acoustic damping material 22 is particularly important because it serves to damp out undesi-rable highs, `as clicks, pops, finger noise and the like, and yalso serves to acoustically isolate the crystals 20 from one another.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variation -of the details of construction which are specifically illustrated `and described may be resorted to without departing from the -true spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. In a transducer bridge for a stringed instrument,

a member having a flat base,

a plurality of cantilever arms extending parallel to said base,

each of said cantilever arms including a string locating element,

a piezo-electric crystal located intermediate each of said cantilever arms and said flat base, and in contact with said cantilever arms,

a layer of electrically conductive material underlying and in contact with said piezo-electric crystals,

an electrical and acoustic insulating layer underlying said layer of electrically conductive material, 'and Ia further layer of electrically conductive material underlying said electrical and acoustic insulating layer land in contact with said base.

2. The combination -according to claim 1 wherein is provided an adjustable spacer supporting said base,

said spacer including two threaded pins,

said base including two holes,

said pins extending freely through said holes, and

nuts threadedly engaging said threaded pins,

each of said nuts including a tapered riser pivotably engaging an edge of one of each hole.

4 3. The combination according to claim 1 wherein said string locating elements are elements slidably adjustable with respect to said base in the direction yof the strings of said guitar.

4. The combination according t-o claim 2 wherein said string locating elements are slidably adjustable with respect to the base in the direction of the strings of said guitar.

5. In a transducer bridge for a stringed instrument,

a base,

means supporting said base on said stringed instrument,

a plurality of descrete cantilever arms secured to said base in string supporting relation, each of said cantilever arms including a string locating element,

a separate piezo-electrical element located in vibration receiving relation to each of said cantilever arms, and means for deriving voltages from said piezo-electric elements which are developed in response to vibrations of said strings and are communicated to said piezo-electric elements via said cantilever larms.

6. The combination according to claim 5, wherein said piezo-electric elements each has two faces, one of said faces being subjected to vibrations provided by said cantilever arms, land means for substantially isolating the other of said faces from vibrations of said base, said other of said faces being supported against said base.

7. The combination according to claim 6 wherein said last means includes a layer of electric and acoustic insulating layer underlying said other of s-aid faces.

8. The combination according to claim 5 wherein is provided an adjustable spacer supporting said base,

said spacer including two threaded pins,

said base including two holes,

said pins extending freely vthrough said holes, and

nuts threadedly engaging said threaded pins,

each of said nuts including a tapered riser pivotably engaging an edge of one of each hole.

9. The combination according to claim 5 wherein said string locating elements are elements slidably adjustable with respect to said base in the direction of the strings of said guitar.

10. The combination according to claim 8 wherein said string locating elements are slidably adjustable with respect to the base in the direction of the strings of said guitar.

References Cited UNITED STATES PATENTS 2,152,783 4/ 1939 Beauchamp 84-1 3,073,202 l/1963 Evans Sli-1.16 3,073,203 1/1963 Evans 84-1.16 3,137,754 6/1964 Evans 84-1.16 3,154,701 10/1964 Evans 84-1.16 3,291,887 12/1966 Carman 84-1.16 3,301,936 1/1967 Carman 3l0-8.7 3,178,501 4/1965 Evans 84-1.16 3,325,580 6/1967 Barcus 310-8 FOREIGN PATENTS 931,689 8/1955 Germany. 1,061,804 4/1954 France.

J. D. MILLER, Primary Examiner. 

1. IN A TRANSDUCER BRIDGE FOR A STRINGED INSTRUMENT, A MEMBER HAVING A FLAT BASE, A PLURALITY OF CANTILIVER ARMS INCLUDING A STRING LOCATING SAID BASE, EACH OF SAID CANTILEVER ARMS INCLUDING A STRING LOCATING ELEMENT, A PIEZO-ELECTRIC CRYSTAL LOCATED INTERMEDIATE EACH OF SAID CANTILEVER ARMS AND SAID FLAT BASE, AND IN CONTACT WITH SAID CANTILEVER ARMS, A LAYER OF ELECTRICALLY CONDUCTIVE MATERIAL UNDERLYING AND IN CONTACT WITH SAID PIEZO-ELECTRIC CRYSTALS, AN ELECTRICAL AN ACOUSTIC INSULATING LAYER UNDERLYING SAID LAYER OF ELECTRICALLY CONDUCTIVE MATERIAL, AND A FURTHER LAYER OF ELECTRICALLY CONDUCTIVE MATERIAL UNDERLYING SAID ELECTRICAL AND ACOUSTIC INSULATING LAYER AND IN CONTACT WITH SAID BASE. 